where the rate of change of varied volume b V is an input, enabling buoyancy-powered propulsion. Note that we have defined a deformable control volume around the vehicle, so that the vehicle’s buoyancy varies, with its mass fixed. Alternatively, one could define a deformable control mass, in which case buoyancy would remain constant and the vehicle mass would vary. If W is greater than zero, the vehicle is heavier than the fluid it displaces and tends to sink, while if W is negative, the vehicle is buoyant and tends to rise.
The